communication problem between two PIC mcs using RF modules

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anandpv2009

Joined: 11 Aug 2009
Posts: 63
Helped: 4
Location: India

20 Sep 2009 17:24 ccs rf

I am trying to communicate two PIC mcs using RF modules.....
I were connected module direcly to pic to TX and RX pins of mc with baud of 500bps.But it does't works properly can any one help me...

RX MC received signals but not correctly.Its urgent because it is related to my main project...

FvM

Joined: 22 Jan 2008
Posts: 5159
Helped: 767
Location: Bochum, Germany

20 Sep 2009 18:03 RF MODULE...Problem

Does the manufacturer specify, that these modules are capable of transmitting UART data? Most simple modules aren't.

anandpv2009

Joined: 11 Aug 2009
Posts: 63
Helped: 4
Location: India

20 Sep 2009 18:10 Re: RF MODULE...Problem

i were bought it from vegakits.

If it is not capable of transmitting UART data? What can i do..
Does it is possible to connect it directly to PIC mc without any other ICs.Because i need high baud rate...If it is possible pls post the Code in ccs/c.

Thanks

pranam77

Joined: 22 Apr 2008
Posts: 1071
Helped: 94
Location: Mangalore(India)

21 Sep 2009 15:46 RF MODULE...Problem

Vega Kit is just a dealer for RF mudules, hobby and robotic kits. Not a manufacturer. All modules he sells are from China. Those modules can be used for remote controlling or low speed data transfer. I doubt about those modules working with high baud rates as "FvM" writes.

anandpv2009

Joined: 11 Aug 2009
Posts: 63
Helped: 4
Location: India

21 Sep 2009 16:14 Re: RF MODULE...Problem

can u explain how to connect a pic directly to the module.Without HT12D/HT12E...

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FvM

Joined: 22 Jan 2008
Posts: 5159
Helped: 767
Location: Bochum, Germany

21 Sep 2009 20:00 RF MODULE...Problem

I have heard different opinions about the feasibility of operating simple RF modules (mostly ASK) with UART signals directly. In my understanding, they have difficulties to handle the large duty cycle range (10 - 90%) involved with UART bitstreams.

Personally, I would always implement manchester encoding and a preamble for synchronisation. Manchester encoding at TX is very easy, the decoding effort at RX depends on, if you can assume an exact bitrate or need to track the transmitter speed. Both can be done in software with a PIC, I think.

thand-s

Joined: 17 Sep 2009
Posts: 4
Location: South Africa

01 Oct 2009 15:31 Re: RF MODULE...Problem

Personally, I would always implement manchester encoding and a preamble for synchronisation. Manchester encoding at TX is very easy, the decoding effort at RX depends on, if you can assume an exact bitrate or need to track the transmitter speed. Both can be done in software with a PIC, I think.[/quote]

you have mentioned that manchester coding would be helpfull on the reciever,please advise on how I would need to code if I'm doing a full Duplex communication between 2 AT8051 0r 8031?

Please advise all you can.